Song Chin-Hee, Kim Nayoung, Choi Yonghoon, Kim Seulgi, Kim Kyung Su, Park Min Hee, Lee Sang Hee, Lee Dong Ho
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea.
Research Center for Sex- and Gender-Specific Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea.
PLoS One. 2025 May 8;20(5):e0323016. doi: 10.1371/journal.pone.0323016. eCollection 2025.
Cow milk contains essential nutrients, with β-casein existing in A1 and A2 forms. Studies suggest that A2 milk (containing only A2 β-casein) may offer gastrointestinal (GI) benefits compared to A1/A2 milk (containing both forms). This study investigated the effects of A2 milk consumption on the gut microbiota of South Korean cohort experiencing GI discomfort after consuming A1/A2 milk. Thirty-five participants with GI discomfort after milk consumption were included. Stool DNA was analyzed using 16S rRNA gene sequencing before and after consuming either A1/A2 or A2 milk. Beta diversity analysis using the generalized UniFrac distance method revealed a significant shift in gut microbiota composition after A2 milk consumption (p = 0.04), but no significant change after consuming A1/A2 milk. Significant differences in gut microbiota composition were found between A1/A2 and A2 milk drinkers after milk consumption (p = 0.031). Alpha diversity indices remained unchanged. Notable increases in beneficial microbes, including Bifidobacterium and Blautia, were observed after A2 milk intake. Linear discriminant analysis Effect Size (LEfSe) analysis identified significant enrichment of Actinobacteria, particularly Bifidobacterium longum and Blautia wexlerae, in the A2 group. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis highlighted enriched transport systems related to energy, peptides, sugars, and raffinose family oligosaccharides in the A2 group. Spearman correlation showed significant associations between Bifidobacterium, Blautia, and enhanced transport systems exclusively in the A2 group. Two weeks of A2 milk consumption led to significant alterations in gut microbiota, promoting beneficial microbes and related functions. A2 milk could be a suitable alternative for subjects who experience milk-intake-related GI discomfort.
牛奶含有必需营养素，其中β-酪蛋白以A1和A2两种形式存在。研究表明，与A1/A2牛奶（同时含有两种形式）相比，A2牛奶（仅含A2β-酪蛋白）可能对胃肠道（GI）有益。本研究调查了饮用A2牛奶对韩国一组饮用A1/A2牛奶后出现胃肠道不适人群肠道微生物群的影响。纳入了35名饮用牛奶后出现胃肠道不适的参与者。在饮用A1/A2牛奶或A2牛奶之前和之后，使用16S rRNA基因测序分析粪便DNA。使用广义UniFrac距离方法进行的β多样性分析显示，饮用A2牛奶后肠道微生物群组成发生了显著变化（p = 0.04），但饮用A1/A2牛奶后无显著变化。饮用牛奶后，A1/A2牛奶饮用者和A2牛奶饮用者之间的肠道微生物群组成存在显著差异（p = 0.031）。α多样性指数保持不变。饮用A2牛奶后，观察到有益微生物显著增加，包括双歧杆菌和布劳特氏菌。线性判别分析效应大小（LEfSe）分析确定A2组中放线菌显著富集，尤其是长双歧杆菌和韦氏布劳特氏菌。未观察状态重建群落系统发育研究（PICRUSt）分析强调A2组中与能量、肽、糖和棉子糖家族寡糖相关的转运系统富集。Spearman相关性显示，仅在A2组中，双歧杆菌、布劳特氏菌与增强的转运系统之间存在显著关联。饮用两周A2牛奶导致肠道微生物群发生显著变化，促进了有益微生物及其相关功能。对于那些饮用牛奶后出现胃肠道不适的人来说，A2牛奶可能是一种合适的替代品。
